Pyrotechnic egress system

ABSTRACT

A pyrotechnic egress system includes an air encapsulation member which at least partially surrounds a charge holder which contains an explosive cord.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with Government support under N00019-06-C-0081 awarded by The United States Navy. The Government has certain rights in this invention.

BACKGROUND

The present disclosure relates to a pyrotechnic egress system, and more particularly to systems which facilitate emergency egress from an aircraft.

Pyrotechnic egress systems explosively sever materials such as aircraft canopy transparencies, egress panels, and other structural members. Operation of this type of system may communicate at least some energy inwards toward the crew in the form of a pressure wave. Furthermore, in aircraft which operate in a maritime environment, the pressure wave may be magnified in an underwater egress situation.

SUMMARY

A pyrotechnic egress system according to an exemplary aspect of the present disclosure includes an air encapsulation member which at least partially surrounds a charge holder which contains an explosive cord.

An explosively severable structure according to an exemplary aspect of the present disclosure includes an explosive cord bonded to a structure. A charge holder which at least partially surrounds the explosive chord. An air encapsulation member which at least partially surrounds the charge holder.

A method of reducing peak pressure and impulse intensity of a pyrotechnic egress system according to an exemplary aspect of the present disclosure includes at least partially surrounding an explosive cord with an air encapsulation member.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a general perspective view of an exemplary rotary wing aircraft embodiment depicting the location of various emergency egress exits;

FIG. 2 depicts an isolated perspective view of a pyrotechnic egress system;

FIG. 3 is a sectional view of the pyrotechnic egress system;

FIG. 4 is a graphical representation of a Pressure and Impulse Measurements from operation of the pyrotechnic egress system compared to operation without an air encapsulation member applied to an explosive cord;

FIG. 5 is a graphical representation of a Pressure and Impulse Measurements from operation of the pyrotechnic egress system Superimposed on Human Injury PI Curves;

FIG. 6 is a sectional view of another embodiment of a pyrotechnic egress system; and

FIG. 7 is a sectional view of another embodiment of a pyrotechnic egress system.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates an exemplary vertical takeoff and landing (VTOL) rotary-wing aircraft 10. The aircraft 10 includes an airframe 14 having an extending tail 16 which mounts an anti-torque system 18. Although a particular helicopter configuration is illustrated and described in the disclosed embodiment, other vehicles, configurations and/or machines, will also benefit herefrom.

The aircraft 10 includes at least one explosively severable structure 20 which are appropriately sized to facilitate rapid egress of passengers/crewmembers in the event of an emergency situation. The explosively severable structure 20, in one non-limiting embodiment, may be a cockpit window 22 adjacent an aircraft cockpit 24 and a cabin window 26 adjacent an aircraft cabin 28.

Referring to FIG. 2, the explosively severable structure 20 is illustrated in an isolated perspective from within the aircraft. The window 22, 26 generally includes a transparency 30 bordered and supported by a panel frame 32. The transparency 30 may be manufactured from, for example, polycarbonate, polycarbonate laminate, acrylic or acrylic/polycarbonate laminates.

A pyrotechnic egress system 40 is located about the periphery of the transparency 30 to essentially separate the transparency from the panel frame 32. It should be understood that the pyrotechnic egress system 40 need not be limited to only a transparency and may be utilized to sever other structures to thereby provide an egress exit therethrough.

The pyrotechnic egress system 40 may be activated through an initiator 42 which is activated from outside the aircraft 10 by pulling a handle 44. The pyrotechnic egress system 40 may also be activated from within the aircraft 10 by pulling a handle 48. The initiator 42 may include boost charges to fire the pyrotechnic egress system 40. It should be understood that although manual activation through pulling of handle 44 or 48 is typical, other activation systems may alternatively or additionally be utilized.

Referring to FIG. 3, the pyrotechnic egress system 40 generally includes an explosive cord 50, a charge holder 52 which at least partially surrounds the explosive chord 50 and an air encapsulation member 54 which at least partially surrounds the charge holder 52.

The explosive cord 50 may include a linear explosive such as, for example, Jetcord®, X-Cord®, Shielded Mild Detonating Cord, TLX®, ITLX® as well as other linear ignition systems. The explosive cord 50 may be bonded directly to the transparency 30 to define a desired egress exit.

The charge holder 52 may include a “U” shaped silicone rubber extrusion that encases the explosive cord 50. The open side of the “U” is directed toward the transparency 30. The charge holder 52 encases and is bonded along the length of the explosive cord 50. The charge holder 52 may also be bonded directly to the transparency 30.

The air encapsulation member 54 may include closed-cell foam such as Styrofoam. In one non-limiting embodiment, the Styrofoam is blue expanded polystyrene manufactured by The Dow Chemical Company of Midland, MI USA. The closed-cell foam contains air which is approximately 10,000 times more compressible and approximately 800 times less dense than water which attenuates the peak pressure wave. Results of the coupon testing indicate that the application of closed-cell foam over the explosive cord 50 significantly reduced peak pressure and impulse intensity levels (FIG. 4).

Referring to FIG. 5, the pyrotechnic egress system 40 utilizes the air encapsulation member 54 to reduce peak pressure and impulse intensity to a level which is considered safe for aircrew and passengers when the pyrotechnic egress assembly is activated in a submerged underwater egress situation. The pyrotechnic egress system 40 thereby facilitates aircraft operations in a maritime environment.

Referring to FIG. 6, another embodiment of the pyrotechnic egress system 40A uses an air encapsulation member 54A with a rectilinear cross-sectional shape. It should be understood that various cross-sectional shapes may alternatively or additionally be utilized.

Referring to FIG. 7, another embodiment of the pyrotechnic egress system 40B uses an air encapsulation member 54B which is at least partially surrounded by a shield 60. The shield 60 may be mounted to the panel frame 32 through a fastener 62. In this non-limiting embodiment, the shield 60 operates primarily to protect the air encapsulation member 54B which may otherwise be exposed to potential damage from within the aircraft cockpit 24 and aircraft cabin 28. The shield 60 further operates to retain the air encapsulation member 54B and explosive cord 50 adjacent to the transparency 30—yet provide a smooth and essentially snag-free boundary about the perimeter thereof

It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.

The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content. 

1. A pyrotechnic egress system for a structure comprising: an explosive cord; a charge holder which at least partially surrounds said explosive chord; and an air encapsulation member which at least partially surrounds said charge holder and abuts the structure.
 2. The system as recited in claim 1, wherein said charge holder is manufactured of a silicone rubber.
 3. The system as recited in claim 1, wherein said charge holder is “U” shaped in cross-section.
 4. The system as recited in claim 1, wherein said air encapsulation member is manufactured of closed-cell foam.
 5. The system as recited in claim 1, wherein said air encapsulation member is manufactured of Styrofoam.
 6. The system as recited in claim 1, wherein said air encapsulation member is rectilinear shaped in cross-section.
 7. An explosively severable structure comprising: a structure; an explosive cord bonded to said structure; a charge holder which at least partially surrounds said explosive chord; and an air encapsulation member which at least partially surrounds said charge holder and abuts said structure.
 8. The structure as recited in claim 7, wherein said structure is transparent.
 9. The structure as recited in claim 7, wherein said structure includes a cockpit window.
 10. The structure as recited in claim 7, wherein said structure includes a cabin window.
 11. The structure as recited in claim 7, wherein said structure includes an escape panel.
 12. The structure as recited in claim 7, wherein said charge holder is “U” shaped in cross-section, an open side of said “U” shape directed toward said structure.
 13. The structure as recited in claim 7, wherein said air encapsulation member is manufactured of a closed-cell foam.
 14. The structure as recited in claim 13, further comprising a shield which at least partially surrounds said air encapsulation member, said shield mounted to said structure.
 15. A method of reducing peak pressure and impulse intensity of a pyrotechnic egress system comprising: at least partially surrounding an explosive cord in contact with a structure with an air encapsulation member, the air encapsulation member in contact with the structure.
 16. A method as recited in claim 15, further comprising at least partially surrounding the explosive cord with a closed-cell foam. 